Nano membrane, method of manufacturing nano membrane, and apparatus for speaker and microphone using nano membrane

ABSTRACT

Disclosed herein is a nano membrane. The nano membrane includes an insulating layer having a thickness corresponding to a diameter of each of metal nanowires and configured to contain the metal nanowires therein, and the metal nanowires arranged to cross and having portions of side surfaces which protrude from one surface of the insulating layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2017-0131633, filed on Oct. 11, 2017 and No.10-2018-0111329, filed on Sep. 18, 2018, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND 1. Field of the Invention

The present invention relates to a conductive nano membrane based on ametal nanowire composite, a method of manufacturing the nano membrane,and a speaker and a microphone using the nano membrane.

2. Discussion of Related Art

With the rapid growth of “Internet of Things (IoT),” which interconnectshumans and machines, personal electronic devices have evolved intosmart, portable, and miniaturized devices. Nonetheless, such personalelectronic devices still hinder tight integration with other electronicdevices in the recent development of wearable devices.

For convenience and appearance, it is necessary to develop wearableelectronic devices with light, versatile, transparent properties. Thistechnological development can create new technologies such as invisibleelectronic devices, skin adhesive electronic skins (electronic skins),and conformal electronic devices.

Particularly, electronic devices using ultra-thin flexible substrateshaving thicknesses in the range of microns are capable of being in closecontact with any surface and provide inconspicuous appearances. Theseelectronic devices can be basically attached to skin and can also bedirectly attached to curved or uneven surfaces having complextopologies.

A free-standing nano membrane (Nano Membrane) having a nano-sizedthickness can provide a robust platform for inconspicuous electronicdevices which provide many features such as a light weight, excellentflexibility, optical transparency, and adaptability. This flexibilitycannot be achieved with conventional bulk materials.

Conventionally, graphene-based conformal devices on micro-polymer nanomembrane substrates have been developed for skin-mounted devices. MoS₂semiconductor-based conformal tactile sensors have also beendemonstrated with high optical transparency and high mechanicalflexibility.

Although the nano membrane-based electronic devices exhibit extremelylow bending stiffness to be capable of being in conformal contact withuneven surfaces, there is a problem in that mechanical properties ofpolymer nano membranes cause mechanical damage by external stress ordeformation due to low fracture toughness.

Unlike polymer nano membranes, hybrid composite nano membranes maycontrol types of loading materials such as metal nanoparticles, metalnanowires, carbon nanotubes, and graphene to provide various electrical,optical, and mechanical properties.

Particularly, since silver nanowires have high electrical, optical, andmechanical properties, the silver nanowires are suitable for hybrid nanomembranes. Further, a conductive silver nanowire network can also beprepared with a cost-effective and large-scale solution-based processincluding spin coating, drop casting, rod coating, or spray coating.

Furthermore, in the past, there has been no attempt to develop alarge-scale conductive silver nanowire composite nano membrane in anelectronic device which can be attached to skin.

SUMMARY OF THE INVENTION

The present invention is directed to an ultra-thin, transparent,conductive, and robust silver nanowire composite nano membrane, whichprovides an inconspicuous appearance through excellent transparency andconformal surface contact ability and is capable of being in contactwith a human body, a speaker and a microphone using the nano membrane,and a method of manufacturing the nano membrane.

According to an aspect of the present invention, there is provided anano membrane including an insulating layer formed to have apredetermined thickness based on a diameter of each of the metalnanowires and contain metal nanowires therein, and the metal nanowiresarranged to cross and having portions of side surfaces which protrudefrom one surface of the insulating layer.

The metal nanowires may be arranged such that the metal nanowires, ofwhich a length direction is arranged in a second direction perpendicularto a first direction, are superimposed on the metal nanowires of which alength direction is arranged in the first direction.

The metal nanowires may be connected in a network structure.

According to another aspect of the present invention, there is provideda method of manufacturing a nano membrane, which includes forming asacrificial layer on a substrate, coating the formed sacrificial layerwith metal nanowires, depositing a polymer coating raw material on thesacrificial layer coated with the metal nanowires and forming aninsulating layer, and removing the sacrificial layer.

The coating the formed sacrificial layer with the metal nanowires mayinclude coating the sacrificial layer with the metal nanowires to directa length direction of each of the metal nanowires in a first direction,and coating the sacrificial layer, which is coated with the metalnanowires, with the remaining metal nanowires to direct a lengthdirection of each of the remaining metal nanowires in a second directionperpendicular to the first direction.

The forming of the insulating layer may include depositing the polymercoating raw material to have a predetermined thickness based on adiameter of each of the metal nanowires to include the metal nanowiresin the deposited polymer coating raw material.

The metal nanowires may be included inside the insulating layer so thata part of a side surface of each of the metal nanowires protrudes fromone surface of the insulating layer.

The removing of the sacrificial layer may include etching thesacrificial layer using a solution by which the sacrificial layer isdissolved.

According to still another aspect of the present invention, there isprovided a speaker device using a nano membrane, which includes theabove-described nano membrane, and a voltage portion configured to applyan alternating current (AC) voltage to the nano membrane.

The voltage portion may change a frequency of the AC voltage everypredetermined period and apply the AC voltage of the changed frequencyto the nano membrane.

The speaker device may further include a frequency measuring portionconfigured to measure a frequency of an input sound signal per timeinterval.

The voltage portion may change a frequency of the AC voltage tocorrespond to the measured frequency and apply the AC voltage of thechanged frequency to the nano membrane.

According to yet another aspect of the present invention, there isprovided a microphone device using a nano membrane, which includes theabove-described nano membrane, a first polymer film bonded to an uppersurface of the nano membrane, and a second polymer film bonded to alower surface of the nano membrane.

The first polymer film may have a flat shape and include a hole passingthrough a flat surface.

The second polymer film may include a plurality of horns regularlyarranged on a surface of the second polymer film, and vertexes of thehorns may be in contact with the lower surface of the nano membrane.

The second polymer film may include a plurality of microdomes regularlyarranged on a surface of the second polymer film, and the plurality ofmicrodomes may be in contact with the lower surface of the nanomembrane.

The second polymer film may include a plurality of micropillarsregularly arranged on a surface of the second polymer film, and theplurality of micropillars may be in contact with the lower surface ofthe nano membrane.

The microphone device may further include a measuring portion configuredto measure an output voltage of triboelectricity and a frequency, whichare generated by vibration of the nano membrane when a sound pressure isapplied to the microphone device.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included as a part of descriptionto help understand the present invention, provide embodiments of thepresent invention and serve to describe the technical features thereoftogether with the description.

FIGS. 1A to 1I are diagrams illustrating a nano membrane according toone embodiment of the present invention.

FIGS. 2A to 2D are diagrams illustrating examples in which the nanomembrane according to one embodiment of the present invention isattached to skin.

FIGS. 3A to 3E are diagrams showing mechanical properties of the nanomembrane according to one embodiment of the present invention.

FIG. 4 is a photograph showing an example of an indentation test formeasuring mechanical properties of the nano membrane according to oneembodiment of the present invention.

FIG. 5 is a diagram illustrating a speaker using the nano membraneaccording to one embodiment of the present invention.

FIGS. 6A to 6E are diagrams showing experimental data of thermalproperties according to an arrangement of silver nanowires with which apolyethylene terephthalate (PET) surface is coated.

FIG. 7 is a graph showing a sound pressure level (SPL) according toinput power of a speaker (NM loudspeaker) using the nano membraneaccording to one embodiment of the present invention and a speaker(Thick film loudspeaker) using a general substrate.

FIG. 8 is a diagram illustrating a case in which a speaker using thenano membrane according to one embodiment of the present invention isattached to a human body.

FIGS. 9A to 9E are diagrams illustrating a microphone using the nanomembrane according to one embodiment of the present invention.

FIGS. 10A to 10C are diagrams showing a comparison of patterns of apolymer film included in the microphone using the nano membraneaccording to one embodiment of the present invention.

FIG. 11 is a diagram showing sound sensing performance of the microphoneusing the nano membrane according to one embodiment of the presentinvention.

FIGS. 12A to 12D are photographs showing a process of removing asacrificial layer of the nano membrane according to one embodiment ofthe present invention.

FIG. 13 is a graph showing a thickness of the nano membrane according toone embodiment of the present invention.

FIG. 14 is a graph showing a comparison of transmittances according tothe number of coating times of a silver nanowire in the nano membraneaccording to one embodiment of the present invention.

FIG. 15 is a schematic cross-sectional view of the nano membraneaccording to one embodiment of the present invention.

FIG. 16 is a scanning electron microscope (SEM) image of the nanomembrane according to one embodiment of the present invention, which iscaptured after the nano membrane is folded in half.

FIG. 17 is a SEM image of the nano membrane according to one embodimentof the present invention, which is captured after the nano membrane isattached to polydimethylsiloxane (PDMS).

FIGS. 18A to 18F are diagrams showing a step surface coverage of apyramid pattern arranged on a surface of PDMS according to the thicknessof the nano membrane in the microphone using the nano membrane accordingto one embodiment of the present invention.

FIG. 19 shows a comparison result of a capillary wrinkle test for thenano membrane according to one embodiment of the present invention and anano membrane made of only parylene.

FIGS. 20A to 20D are graphs showing a result of a hysteresis indentationload test (loading-unloading indentation test) for the nano membraneaccording to one embodiment of the present invention and a nano membranemade of only a polymer.

FIGS. 21A and 21B are graphs showing a theoretical comparison of SPLsfor the speaker using the nano membrane according to one embodiment ofthe present invention and a speaker including a PET substrate having ageneral thickness.

FIGS. 22A and 22B are diagrams illustrating a comparison of themicrophone using the nano membrane according to one embodiment of thepresent invention and a microphone including a planar polymer film.

FIGS. 23A to 23C show a result for which the microphone using the nanomembrane according to one embodiment of the present invention isemployed in a voice pattern security system.

FIG. 24 is a graph showing a result of a comparison test for themicrophone using the nano membrane according to one embodiment of thepresent invention and a commercial microphone.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The terms a first, a second, and/or the like in this disclosure are usedonly for the purpose of distinguishing one component from anothercomponent. That is, components are not intended to be limited to theseterms.

Components, features, and steps, which are referred to as “beingincluded” in this disclosure, mean the presence of correspondingcomponents, features, and steps and do not preclude the presence of oneor more other components, features, steps, and equivalents thereof.

Unless the context clearly dictates otherwise, the singular formincludes the plural form. That is, the components and the like referredto in this disclosure may mean the presence or addition of one or moreother components or the like.

Unless defined otherwise, all terms including technical or scientificterms used herein have the same meaning as commonly understood by thoseskilled in the art (ordinary skilled persons) to which the presentinvention pertains.

That is, general terms that are defined in a dictionary shall beconstrued to have meanings that are consistent in the context of therelevant art, and will not be interpreted as having an idealistic orexcessively formalistic meaning unless clearly defined in thisdisclosure.

Hereinafter, a nano membrane according to embodiments of the presentinvention, a method of manufacturing the nano membrane, and a speakerand microphone using the nano membrane will be described in detail withreference to the accompanying drawings.

FIGS. 1A to 1I are diagrams illustrating a nano membrane according toone embodiment of the present invention.

Specifically, FIG. 1A is a diagram illustrating a process ofmanufacturing the nano membrane according to one embodiment of thepresent invention.

The process of manufacturing a nano membrane according to one embodimentof the present invention may include forming a sacrificial layer on asubstrate, coating the deposited sacrificial layer with metal nanowires,forming an insulating layer by depositing an insulating polymer coatingraw material on the sacrificial layer coated with the metal nanowires,and removing the sacrificial layer.

The forming of the sacrificial layer on the substrate may includeforming the sacrificial layer, which will be removed later, on thesubstrate, and for example, the sacrificial layer may be formed bydepositing zinc oxide (ZnO) on a silicon (Si) substrate.

The coating of the deposited sacrificial layer with the metal nanowiresincludes coating the sacrificial layer with silver nanowires throughsolution-based bar-coating.

The coating of the deposited sacrificial layer with the metal nanowiresincludes coating the deposited sacrificial layer with the metalnanowires to direct a length direction of each thereof in a firstdirection and coating the sacrificial layer, which is coated with themetal nanowires, with the remaining metal nanowires to direct a lengthdirection of each of the remaining metal nanowires in a second directionperpendicular to the first direction.

That is, the metal nanowires of which a length direction is arranged inthe second direction may be superimposed on the metal nanowires of whicha length direction is arranged in the first direction. The metalnanowires are arranged perpendicular to each other, and since the metalnanowires are coated with a network structure, each of the metalnanowires may be connected to each other.

The forming of the insulating layer by depositing the insulating polymercoating raw material on the sacrificial layer coated with the metalnanowires includes forming an insulating layer by depositing parylene-C,which is a polymer coating raw material, on the sacrificial layer coatedwith the metal nanowires.

The insulating layer may be formed to have a predetermined thicknessbased on a diameter of each of the metal nanowires. That is, since aheight of a portion at which the metal nanowires intersect is higherthan the diameter of each of the metal nanowires, the insulating layermay be formed to have a thickness in consideration of the height of theportion, at which the metal nanowires intersect, corresponding to thediameters of the metal nanowires.

For example, the insulating layer may be formed to have a thickness inthe range of the height of the portion, at which the metal nanowiresintersect, to 100 nm.

The metal nanowires may be included inside the insulating layer so thata portion of a side surface of each of the metal nanowires may protrudefrom one surface of the insulating layer.

The removing of the sacrificial layer includes etching the sacrificiallayer using a solution by which the sacrificial layer is dissolved. Forexample, the sacrificial layer may be etched using a citric acidsolution (10 wt % in water) to obtain a silver nanowire composite nanomembrane (hereinafter referred to as a nano membrane) separated from theSi substrate.

FIG. 1B is a photograph showing a nano membrane deposited on thesacrificial layer, and FIG. 1C is a photograph showing a nano membranefrom which the sacrificial layer is etched.

The nano membrane deposited on the sacrificial layer is floated on thecitric acid solution and the ZnO sacrificial layer is dissolved by thecitric acid solution such that the Si substrate and the nano membranemay be separated.

FIG. 1D is a photograph showing a dark field optical microscope imageand a Fast Fourier Transform (FFT) image of a cross-aligned silvernanowire array. Referring to FIG. 1D, it can be seen that the silvernanowires are highly aligned with a cross structure.

FIG. 1E is a cross-sectional scanning electron microscope (SEM) image ofthe nano membrane deposited on the sacrificial layer. Referring to FIG.1E, a polymer coating raw material may be deposited with a thickness of100 nm or less on the sacrificial layer.

FIG. 1F is a graph showing average optical transmittance of each of aconventional nano membrane, the nano membrane according to oneembodiment of the present invention, polyethylene terephthalate (PET),and glass in a visible light wavelength range of 400 nm to 800 nm.

Referring to FIG. 1F, in the visible light wavelength range of 400 nm to800 nm, the average optical transmittance of the conventional nanomembrane (Pure NM) not containing silver nanowires is about 98.2%, theaverage optical transmittance of the PET is about 92.9%, and the averageoptical transmittance of the glass (Glass) is about 93.5%.

The average optical transmittance of the nano membrane (Hybrid NM)according to one embodiment of the present invention was measured to behigher than the average optical transmittances of the PET and the glassin the visible light wavelength range of 550 nm to 800 nm.

FIG. 1G is a photograph showing a nano membrane supported by a wireloop.

Referring to FIG. 1G, an inset is an enlarged view of a photographcaptured through the nano membrane according to one embodiment of thepresent invention.

The nano membrane according to one embodiment of the present inventionis optically transparent, and the silver nanowires are arrangedorthogonally therein to provide high electrical conductivity.

FIG. 1H is a photograph showing a nano membrane attached to a curvedsurface, and FIG. 1I is a photograph showing a nano membrane attached toa human body.

The nano membrane according to one embodiment of the present inventionis transparent and is capable of being freely attached to any substratehaving a curved and complex surface without mechanical damage.

FIGS. 2A to 2D are diagrams illustrating examples in which the nanomembrane according to one embodiment of the present invention isattached to skin.

Specifically, FIG. 2A is a schematic diagram illustrating a case inwhich a nano membrane is attached to a surface of skin, and FIG. 2B is aphotograph showing a nano membrane attached to a thumb.

Referring to FIGS. 2A and 2B, the nano membrane according to oneembodiment of the present invention may provide a high level ofbendability due to very low bending stiffness resulting from a nanoscalethickness and may be easily attached to a three-dimensional (3D)surface.

That is, since the nano membrane according to one embodiment of thepresent invention may be suitably adhered to human skin having a curvedand uneven complex topography, there is an advantage in that the nanomembrane is capable of being applied to a wearable appliance.

FIGS. 2C and 2D are SEM images of the nano membrane according to oneembodiment of the present invention, which are captured after the nanomembrane is attached to each of line pattern 3D polydimethylsiloxane(PDMS) fine structures having widths of 20 μm and 120 μm.

In order to further study a conformal contact of the nano membrane inthe 3D fine structure, the nano membrane according to one embodiment ofthe present invention was transferred to each of a PDMS surface havingline widths of 20 μm and 120 μm. The nano membrane was in conformalcontact with the line pattern of the 3D PDMS fine structure along anedge of each of line patterns of the PDMS, and this exhibits that thenano membrane according to one embodiment of the present invention hashigh bendability due to low bending stiffness.

FIGS. 3A to 3E are diagrams showing mechanical properties of the nanomembrane according to one embodiment of the present invention.

Specifically, FIG. 3A is photographs showing a result of a capillarywrinkle test for measuring wrinkles on a surface of the nano membrane,which are caused by a droplet falling on the surface, according todensity of silver nanowires.

In order to measure Young's modulus of the nano membrane according toone embodiment of the present invention, a capillary wrinkle test wasperformed such that a water droplet was placed at centers of a purepolymer (Only parylene), a nano membrane (Orthogonal×1), a nano membrane(Orthogonal×2) having a density of silver nanowires two times that ofthe nano membrane (Orthogonal×1), and a nano membrane (Orthogonal×3)having a density of silver nanowires three times that of the nanomembrane (Orthogonal×1).

When the water droplet falls at the center of the nano membrane,wrinkles are formed on the surface of the nano membrane by a capillaryforce, and the number of the wrinkles formed on the nano membranedecreases as a density of the cross-aligned silver nanowires increases.That is, it was confirmed that Young's modulus of the nano membraneincreases as the density of the silver nanowires increases.

FIG. 3B is a graph showing the number of wrinkles on the surface of thenano membrane caused by a water droplet.

Referring to FIG. 3B, in order to further research an effect of across-aligned silver nanowire array on the Young's modulus of the nanomembrane, the number of wrinkles N of the nano membrane is representedby a function of a^(1/2)h^(−3/4), wherein a is a radius of the waterdroplet and h is a thickness of the nano membrane.

Elastic modulus of the nano membrane may be calculated according to thefollowing Equation 1.

$\begin{matrix}{N = {{C_{N}\left\lbrack \frac{12\left( {1 - \Lambda^{2}} \right)\gamma}{E} \right\rbrack}^{1/4}a^{1/2}h^{{- 3}/4}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Here, Λ is a Poisson's ratio, γ is surface tension of the water droplet,E is Young's modulus of the nano membrane, and C_(N) is a coefficient.In the graph of FIG. 3B, the coefficient C_(N) was calculated as 3.2.

FIG. 3C is a graph showing the Young's modulus of the nano membraneaccording to the density of the silver nanowires calculated through thewrinkle test.

Referring to FIG. 3C, as the number of orthogonally-arranged silvernanowires (Number of orthogonal AgNW array) increases, the Young'smodulus of the nano membrane increases linearly.

FIG. 3D is a graph showing an indentation load (Load) with respect to adisplacement of the nano membrane according to a density of across-aligned silver nanowire array.

Referring to FIG. 3D, the nano membrane had an indentation load higherthan that of a pure polymer (Only parylene NM), and among the nanomembranes, the indentation load was measured to be higher as the densityof the silver nanowires increases.

FIG. 3E is a graph showing a maximum indentation load (Maximum load)with respect to a maximum displacement (Maximum displacement) of thenano membrane according to the density of the silver nanowires.

Referring to FIG. 3E, the maximum indentation load of the nano membraneaccording to one embodiment of the present invention is graduallyincreased as a density of an orthogonally-arranged silver nanowire arrayincreases.

A maximum indentation load of a nano membrane (Orthogonal array×3)having a largest density of the silver nanowires was about 85 mN, and amaximum indentation load of a nano membrane (only parylene NM), whichcontains only parylene but no silver nanowires, was about 45 mN so thatit was confirmed that a difference in maximum indentation load of thenano membrane was about twice according to whether theorthogonally-arranged silver nanowires are contained.

An effective interface is possible due to efficient mechanicalreinforcement of an orthogonally-arranged silver nanowire network suchthat an efficient load transfer inside a polymer matrix in a nanocomposite material system is induced. These results suggest that theorthogonally-arranged silver nanowires may become a good loadingmaterial for improving mechanical properties of the nano membrane.

FIG. 4 is a photograph showing an example of an indentation test formeasuring mechanical properties of the nano membrane according to oneembodiment of the present invention.

Referring to FIG. 4, in order to measure mechanical toughness of thenano membrane according to one embodiment of the present invention, atest was performed to measure an indentation load according to a densityof the cross-aligned silver nanowire array. For the indentation loadmeasuring test, the nano membrane according to one embodiment of thepresent invention was attached to a support plate with a hole having adiameter of 10 mm, and a force was applied by a metal rod to deform andmeasure a maximum load limit of the nano membrane.

FIG. 5 is a diagram illustrating a speaker using the nano membraneaccording to one embodiment of the present invention.

Referring to FIG. 5, the speaker using the nano membrane according toone embodiment of the present invention is capable of being easilyattached to a human body with, e.g., a thickness of 100 nm or less to beapplied to a wearable speaker.

The speaker using the nano membrane according to one embodiment of thepresent invention may include a voltage portion for applying analternating current (AC) voltage to the nano membrane.

The voltage portion may change a frequency of the AC voltage everypredetermined period and apply the AC voltage having the changedfrequency to the nano membrane.

In addition, the speaker using the nano membrane according to oneembodiment of the present invention may further include a frequencymeasuring portion for measuring a frequency of an input sound signal pertime interval.

The frequency measuring portion may measure the frequency of the inputsound signal per time interval, and the voltage portion may change thefrequency of the AC voltage to correspond to the measured frequency toapply the AC voltage of the changed frequency to the nano membrane.

For example, when the voltage portion applies AC voltages of the samefrequency to the nano membrane, the same sound is output from the nanomembrane, and when the voltage portion applies an AC voltage to the nanomembrane while changing a frequency of the AC voltage to correspond tothe frequency measured by the frequency measuring portion, a music soundmay be output.

In the speaker using the nano membrane according to one embodiment ofthe present invention, ambient air expands and contracts due to heatgenerated by applying an AC voltage to the nano membrane so thatvibration occurs to cause acoustic emission.

That is, when an AC voltage is applied to the speaker using the nanomembrane according to one embodiment of the present invention, jouleheat is generated by resistance generated in metal nanowires included inthe nano membrane, and ambient air vibrates while expanding andcontracting due to the generated joule heat to cause emission of athermoacoustic sound.

FIGS. 6A to 6E are diagrams showing experimental data of thermalproperties according to an arrangement of silver nanowires with which aPET surface is coated.

FIGS. 6A and 6B are photographs capturing, by an infrared camera, jouleheat characteristics of silver nanowires orthogonally-arranged on asurface of PET (hereinafter referred to as rectangular silver nanowires)and silver nanowires randomly arranged on the surface of the PET(hereinafter referred to as random silver nanowires).

Referring to FIGS. 6A and 6B, when the same direct-current (DC) voltageis applied, it was confirmed that the rectangular silver nanowires havea uniform thermal distribution and an improved joule heat performancecompared to the random silver nanowires.

Due to contact points between the silver nanowires which areorthogonally-arranged and uniformly distributed and a low percolationthreshold value according to the cross-aligned silver nanowire array, itwas confirmed that the thermal distribution and the joule heatperformance of the rectangular silver nanowires were improved more thanthose of the random silver nanowires.

Particularly, since the thermal distribution of the random silvernanowires is not uniform, “hot spots” may be brought about to causedegradation of the joule heat performance.

FIG. 6C is a photograph capturing, by an infrared camera, a joule heatcharacteristic of a rectangular silver nanowire network in which silvernanowires are orthogonally-arranged when an AC voltage of 10 V having afrequency of 10 kHz is applied.

Referring to FIG. 6C, since the silver nanowires are orthogonallyarranged in the rectangular silver nanowires and thus the thermaldistribution is uniform to not cause “hot spots,” there is an advantagein that the joule heat performance is not degraded.

FIGS. 6D and 6E are graphs showing changes over time in temperature whena DC voltage is applied to each of the rectangular silver nanowires andthe random silver nanowires.

Referring to FIGS. 6D and 6E, temperature profiles of the rectangularsilver nanowires and the random silver nanowires were measured while theapplied DC voltage is varied in the range of 3V to 10V.

As can be seen from the measured temperature profiles, the rectangularsilver nanowires exhibited joule heat performance much higher than thatof the random silver nanowires due to an effective current flow througha uniform conductive network and the low percolation threshold value.

In order to calculate heat generated by the silver nanowire network,Joule's law was used and a saturation temperature T_(s) of the silvernanowire network may be calculated according to the following Equation2.

$\begin{matrix}{T_{s} = {\frac{{U^{2}t\text{/}R} - Q_{d}}{Cm} + T_{i}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Here, T_(i) is an initial temperature, U is an applied voltage, t is aheating time, R is resistance of a heated film, Q_(d) is dissipationheat, C is a heat capacity ratio of the heated film, and m is a mass ofthe heated film.

It was measured that a mass (or a percolation threshold value) of silvernanowires in the heated film affected heat dissipation performance ofthe silver nanowire network.

Referring to FIGS. 6A to 6E, when the same voltage is applied, atemperature of the rectangular silver nanowires rises uniformly fasterthan that of the random silver nanowires, and thus it can be seen thatthe heat dissipation performance of the rectangular silver nanowires issuperior to that of the random silver nanowires.

That is, when the same voltage is applied for the same time, therectangular silver nanowires radiate a larger amount of heat than therandom silver nanowires.

Consequently, since the speaker using the nano membrane according to oneembodiment of the present invention heats ambient air better than aspeaker using a nano membrane in which silver nanowires are randomlyarranged, it can be seen that sound output performance in which a soundis generated by vibration of the ambient air is more excellent.

FIG. 7 is a graph showing a sound pressure level (SPL) according toinput power of a speaker (NM loudspeaker) using the nano membraneaccording to one embodiment of the present invention and a speaker(Thick film loudspeaker) using a general substrate.

Referring to FIG. 7, a measured SPL (NM loudspeaker_exp.) of the speaker(NM loudspeaker) using the nano membrane according to one embodiment ofthe present invention is measured to be higher than a theoretical SPL(NM loudspeaker_theo.) at a frequency of about 13 kHz or less.

On the other hand, a measured SPL (Thick film loudspeaker_exp.) of thespeaker (Thick film loudspeaker) using a general substrate having athickness of about 220 μm was measured to be lower than a theoreticalSPL (NM loudspeaker_theo.) at a frequency of about 3 kHz or more.

Further, it was confirmed that the sound pressure output performance ofthe speaker (NM loudspeaker) using the nano membrane according to oneembodiment of the present invention was improved more than the soundpressure output performance of the speaker using the general substrate(Thick film loudspeaker).

When an AC voltage is applied, the speaker (NM loudspeaker) using thenano membrane according to one embodiment of the present invention mayminimize a loss of resistance heat generated by the silver nanowires dueto the orthogonally-arranged silver nanowires and an ultra-thin filmthickness of about 100 nm, thereby providing improved sound pressureperformance over all sound frequency ranges more than a speaker using asubstrate having a general thickness of 220 μm.

FIG. 8 is a diagram illustrating a case in which a speaker using thenano membrane according to one embodiment of the present invention isattached to a human body.

Referring to FIG. 8, the nano membrane according to one embodiment ofthe present invention may provide a high level of bendability due tovery low bending stiffness resulting from a nanoscale thickness and maybe easily attached to a 3D surface such as skin.

FIGS. 9A to 9E are diagrams illustrating a microphone using the nanomembrane according to one embodiment of the present invention.

Specifically, FIG. 9A is a diagram illustrating a triboelectric sounddetection mechanism of a microphone using the nano membrane according toone embodiment of the present invention.

Referring to FIG. 9A, the microphone using the nano membrane accordingto one embodiment of the present invention may include a nano membrane,a first polymer film bonded to an upper surface of the nano membrane,and a second polymer film bonded to a lower surface of the nanomembrane. Further, the microphone may further include a measuringportion for measuring an output voltage of triboelectricity and afrequency thereof, which are generated by vibration of the nano membranewhen a sound pressure is applied to the microphone using the nanomembrane according to one embodiment of the present invention.

For example, the first and second polymer films may be PDMS films, andthe microphone according to one embodiment of the present invention mayhave a sandwich structure in which the first polymer film, the nanomembrane, and the second polymer film are bonded. At this point, one ofboth surfaces of the nano membrane, on which the silver nanowires arelocated, may be in contact with and coupled to the second polymer film.

The first polymer film may have a flat shape and may include a holepassing through a flat surface.

The second polymer film may include either of a plurality of horns,microdomes, or micropillars, which are regularly arranged on a surfaceof the second polymer film.

For example, when a plurality of horns are arranged on the surface ofthe second polymer film, vertexes of the horns may be brought intocontact with the lower surface of the nano membrane. Similarly, when aplurality of microdomes or micropillars are arranged on the surface ofthe second polymer film, the plurality of microdomes or micropillars maybe brought into contact with the lower surface of the nano membrane.When a sound pressure is transmitted to the nano membrane through thehole of the first polymer film, the nano membrane may vibrate and rubagainst the vertexes of the horns of the second polymer film whilevibrating to generate a triboelectric signal. The measuring portion maymeasure the generated triboelectric signal to analyze a waveform of thegenerated triboelectric signal, and an AC signal corresponding to theanalyzed waveform may be generated.

FIGS. 9B and 9C are graphs showing test data of measuring outputvoltages of triboelectricity of a microphone (NM microphone) including asecond polymer film having micropyramids arranged on a surface of thesecond polymer film and a microphone (Planar film microphone) includinga second polymer film having a flat surface according to a frequency andan SPL.

Referring to FIG. 9B, when the same frequency is input, the outputvoltage of the triboelectricity generated in the microphone (NMmicrophone) was measured to be larger than the output voltage of thetriboelectricity generated in the microphone (Planar film microphone).

Referring to FIG. 9C, when the same SPL is input, the output voltage ofthe triboelectricity generated in the microphone (NM microphone) wasmeasured to be larger than the output voltage of the triboelectricitygenerated in the microphone (Planar film microphone).

That is, since the second polymer film having the flat surface is instrong contact with the nano membrane, vibration of a nano membraneincluded in the microphone (Planar film microphone) may occur less thanvibration of a nano membrane included in the microphone (NM microphone).

Since the output voltage of the triboelectricity is increased as thevibration occurs greatly and the microphone becomes excellent in sounddetection performance as the output voltage of the triboelectricity isincreased, it was confirmed that the sound detection performance of themicrophone (NM microphone) including the second polymer film having aflat surface is superior to the sound detection performance of themicrophone (Planar film microphone).

FIG. 9D is a graph showing waveforms and short-time Fourier transforms(STFTs) of input signals when the same sounds are input to aconventional sound wave analyzer (left), the microphone (NM microphone)(center), and the microphone (Planar film microphone) (right).

Referring to FIG. 9D, when a sentence of “There's plenty of room at thebottom” is input to the conventional sound wave analyzer, the microphone(NM microphone), and the microphone (Planar film microphone), a waveformand a spectrogram of the output voltage from the conventional sound waveanalyzer coincided with those of the output voltage from the microphone(NM microphone).

However, the waveforms and the spectrograms of the output voltages ofthe conventional sound wave analyzer and the microphone (Planar filmmicrophone) were measured very differently, and it was confirmed thatthe sound detection performance of the microphone (NM microphone) issuperior to the sound detection performance of the microphone (Planarfilm microphone) through the test.

FIG. 9E is a diagram illustrating an example of performing a sounddetection test by attaching the microphone using the nano membraneaccording to one embodiment of the present invention to a human body.

Like the nano membrane according to one embodiment of the presentinvention, since the microphone using the nano membrane is based on athin elastic polymer PDMS film, the microphone may be easily attached toa curved 3D surface like the human body.

Further, since all the nano membrane and the polymer film aretransparent, there is an advantage of not disturbing a field of viewfield even when the microphone is attached to a neck of human.

FIGS. 10A to 10C are diagrams showing a comparison of patterns of apolymer film included in the microphone using the nano membraneaccording to one embodiment of the present invention.

FIG. 10A is a diagram illustrating a surface pattern of the secondpolymer film included in the microphone using the nano membraneaccording to one embodiment of the present invention.

Referring to FIG. 10A, either of microdomes, micropillars, ormicropyramids may be regularly arranged on the surface of the secondpolymer film.

FIG. 10B is a conceptual diagram for measuring an adhesion force betweenthe first and second polymer films.

FIG. 10C is a graph showing test data measuring the adhesion forcebetween the first and second polymer films.

Referring to FIG. 10C, the surface of the second polymer film of themicrophone using the nano membrane according to one embodiment of thepresent invention has a flat structure, a micropillar structure, amicrodome structure, or a micropyramid structure, an adhesion force ofthe second polymer film in each of the flat structure, the micropillarstructure, the microdome structure, and the micropyramid structureagainst the first polymer film having a flat structure was measured.

When the second polymer film having the flat structure was bonded to thefirst polymeric film, the adhesion force was measured to be highest atabout 20.8 seconds because the first polymer film and the second polymerfilm adhered to each other and did not fall off easily.

In the case of the surface of the second polymer film having themicropillar structure, the microdome structure, or the micropyramidstructure, an adhesion force was measured to be lower than that of thesecond polymer film with the surface having the flat structure.Particularly, the adhesion force of the second polymer film with thesurface having the micropyramid structure was measured to be lowest, andthus performance of the second polymer film with the surface having themicropyramid structure was measured to be superior to performance of thesecond polymer films having the micropillar structure and the microdomestructure.

FIG. 11 is a diagram showing sound sensing performance of the microphoneusing the nano membrane according to one embodiment of the presentinvention.

Referring to FIG. 11, when the microphone using the nano membraneaccording to one embodiment of the present invention is attached to aneck and then “A,” “B,” “C,” and “D” are said, it was confirmed thateach voice was clearly sensed by the microphone.

FIGS. 12A to 12D are photographs showing a process of removing asacrificial layer of the nano membrane according to one embodiment ofthe present invention.

As shown in FIG. 12A, when a ZnO sacrificial layer is formed on the Sisubstrate and a nano membrane formed on the ZnO sacrificial layer isfloated in an etchant solution, the ZnO sacrificial layer is dissolvedby the etchant solution with the passage of time as shown in FIG. 12B,and when the ZnO sacrificial layer is completely dissolved and removed,the Si substrate and the nano membrane are separated from each other asshown in FIG. 12C.

FIG. 12D is a SEM image captured by attaching the nano membrane to ananodic aluminum oxide (AAO) mold. A size of a scale bar is 500 nm.

FIG. 13 is a graph showing a thickness of the nano membrane according toone embodiment of the present invention.

Referring to FIG. 13, a thickness of the nano membrane was measured tobe about 100 nm using an atomic force microscopy.

Since the nano membrane according to one embodiment of the presentinvention has a thin thickness of about 100 nm, the nano membrane hasstrong bendability such that there is an advantage in that an adhesionforce to a human body, a curved surface, and the like is excellent.

Further, owing to the thin thickness of the nano membrane, the speakerand the microphone, which use the nano membrane, may also have excellentadhesion forces to the human body such that there is an advantage inthat the speaker and the microphone are capable of being applied to awearable device.

FIG. 14 is a graph showing a comparison of transmittances according tothe number of coating times of a silver nanowire in the nano membraneaccording to one embodiment of the present invention.

Referring to FIG. 14, it can be seen that, as the number of coatingtimes of the silver nanowires increases (the number of orthogonal arraysincreases) in a wavelength range of 400 nm to 800 nm, transmittancedecreases.

FIG. 15 is a schematic cross-sectional view of the nano membraneaccording to one embodiment of the present invention.

Referring to FIG. 15, n silver nanowires of which has a radius r and aYoung's modulus of 83 GPa are included in a parylene thin film having asize of b×h and a Young's modulus of 3.2 GPa.

A distance y₀ between a neutral axis and a bottom of the parylene thinfilm is calculated according to the following Equation 3.

$\begin{matrix}{y_{0} = {\frac{h}{2} \star \frac{1 + {\frac{{2h} + {2r}}{h}\left( {\frac{E_{Ag}}{E_{Pa}} - 1} \right)n\;\pi\;{r^{2}/{bh}}}}{1 + {\left( {\frac{E_{Ag}}{E_{Pa}} - 1} \right)n\;\pi\;{r^{2}/{bh}}}}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Here, y₀ is the distance between the neutral axis and the bottom of theparylene thin film, h is a thickness of the parylene thin film, h′ is adistance between the silver nanowires and the bottom of the parylenethin film, r is a radius of each of the silver nanowires, b is a widthof the parylene thin film, and E_(Ag) and E_(Pa) are Young's moduli ofthe silver nanowire and the parylene thin film, respectively.

On the basis of y₀ calculated according to Equation 3, bending stiffnessof the nano membrane may be calculated using the following Equation 4.EI=E _(Pa) bh(⅓h ² −hy ₀ +y ₀ ²)+(E _(Ag) −E _(Pa))nπr ²[4/3r ²+2r(h′−y₀)+(h′−y ₀)²]  [Equation 4]

Here, y₀ is the distance between the neutral axis and the bottom of theparylene thin film, h is a thickness of the parylene thin film, h′ is adistance between the silver nanowires and the bottom of the parylenethin film, r is a radius of each of the silver nanowires, b is a widthof the parylene thin film, and E_(Ag) and E_(Pa) are Young's moduli ofthe silver nanowire and the parylene thin film, respectively.

Aside from Equation 4, on the basis of y₀ calculated according toEquation 3, the bending stiffness of the nano membrane may also becalculated even using the following Equation 5.EI=E _(hybrid) bh(⅓h ² −hy ₀ +y ₀ ²)  [Equation 5]

Here, E_(Hybrid) is a Young's modulus of a nano membrane containingorthogonally-arranged silver nanowires and was experimentally calculatedthrough the capillary wrinkle test of FIG. 3A.

FIG. 16 is an SEM image of the nano membrane according to one embodimentof the present invention, which is captured after the nano membrane isfolded in half.

Referring to FIG. 16, the nano membrane folded in half has a bendingradius of 2.2 μm or less. A size of a scale bar on an upper left side inFIG. 16 is 5 μm, and a size of a scale bar included in an inset is 1 μm.

FIG. 17 is a SEM image of the nano membrane according to one embodimentof the present invention, which is captured after the nano membrane isattached to PDMS.

Referring to FIG. 17, the nano membrane was closely adhered along anedge of a line pattern of a surface of PDMS having a width of 20 μm. Asize of a scale bar is 10 μm.

FIGS. 18A to 18F are diagrams showing a step surface coverage of apyramid pattern arranged on a surface of PDMS according to the thicknessof the nano membrane in the microphone using the nano membrane accordingto one embodiment of the present invention.

FIG. 18A is a pyramidal pattern of PDMS to which the nano membrane isnot attached, and FIGS. 18B to 18D are pyramidal patterns of PDMS towhich nano membranes having thicknesses of 40 nm, 100 nm, and 200 nm,respectively, are attached.

FIG. 18E is a conceptual diagram for calculating a step surface coverageof the pyramid pattern arranged on the surface of PDMS.

Referring to FIG. 18E, the step surface coverage of the pyramid patternmay be calculated as h/h₀*100. Here, h is a height covered by the nanomembrane, and h₀ is a height of the pyramid pattern when the nanomembrane is not attached.

FIG. 18F is a graph showing a calculated step surface coverage of thepyramid pattern arranged on the surface of PDMS per thickness of thenano membrane.

Referring to FIG. 18F, the step surface coverage of the pyramid patternarranged on the surface of PDMS was measured to be higher as thethickness of the nano membrane becomes thinner.

That is, it was experimentally confirmed that, as the thickness of thenano membrane becomes thinner, adhesion forces of the nano membraneaccording to one embodiment of the present invention, the speaker usingthe nano membrane, and the microphone using the nano membrane wereimproved to a 3D surface such that the nano membrane, the speaker usingthe nano membrane, and the microphone using the nano membrane may bewell attached to a human body or a curved surface.

FIG. 19 shows a comparison result of a capillary wrinkle test for thenano membrane according to one embodiment of the present invention and anano membrane made of only parylene.

Referring to FIG. 19, as a result of the capillary wrinkle test, sincethe nano membrane according to one embodiment of the present inventionincludes the orthogonally-arranged silver nanowires, the number ofcapillary wrinkles was exhibited to be smaller than that of the nanomembrane made of only parylene.

Since the silver nanowires are included, the Young's modulus of the nanomembrane was increased, and additionally, referring to FIG. 3A, it canbe seen that, since the number of capillary wrinkles is decreased as thedensity of the silver nanowires increases, the Young's modulusincreases.

FIGS. 20A to 20D are graphs showing a result of a hysteresis indentationload test (loading-unloading indentation test) for the nano membraneaccording to one embodiment of the present invention and a nano membranemade of only a polymer.

FIGS. 20A and 20B are hysteresis indentation load test results of thenano membrane (Hybrid NM) according to one embodiment of the presentinvention and a nano membrane (Polymer NM) made of only a polymer whenan indentation load is 27 mN or less.

Referring to FIGS. 20A and 20B, when an indentation load is repeatedlyapplied, measured hysteresis curves of the nano membrane (Polymer NM)made of only a polymer exhibited a similar tendency.

On the other hand, when the indentation load is first applied, the nanomembrane (Hybrid NM) according to one embodiment of the presentinvention exhibited a hysteresis curve having a wider range than thenano membrane (Polymer NM) made of only a polymer, while tendency of thehysteresis curve exhibited a significant change when the indentationload is repeatedly applied.

FIGS. 20C and 20D are hysteresis indentation load test results of thenano membrane (Hybrid NM) according to one embodiment of the presentinvention and the nano membrane (Polymer NM) made of only a polymer whenan indentation load is 11 mN or less.

Referring to FIGS. 20C and 20D, when the indentation load is 11 mN orless, the nano membrane (Hybrid NM) according to one embodiment of thepresent invention and the nano membrane (Polymer NM) made of only apolymer were measured to exhibit a similar tendency.

FIGS. 21A and 21B are graphs showing a theoretical comparison of SPLsfor the speaker using the nano membrane according to one embodiment ofthe present invention and a speaker including a PET substrate having ageneral thickness.

Referring to 21A, when a thickness of a speaker (Parylene film_theo.)using the nano membrane according to one embodiment of the presentinvention and a thickness of a speaker (PET film_theo.) including a PETsubstrate each are 100 nm, SPLs for each frequency are the same.

Referring to FIG. 21B, when the thickness of the speaker (Parylenefilm_theo.) using the nano membrane according to one embodiment of thepresent invention and the thickness of the speaker (PET film_theo.)including the PET substrate each are 220 μm, the SPL of the speaker(Parylene film_theo.) using the nano membrane according to oneembodiment of the present invention was measured to be high.

That is, it was experimentally confirmed that sound emission performanceof the speaker (Parylene film_theo.) using the nano membrane accordingto one embodiment of the present invention was superior to that of thespeaker (PET film_theo.) including the PET substrate.

FIGS. 22A and 22B are diagrams illustrating a comparison of themicrophone using the nano membrane according to one embodiment of thepresent invention and a microphone including a planar polymer film.

FIG. 22A shows the microphone (NM microphone) using the nano membraneaccording to one embodiment of the present invention, and FIG. 22B showsa microphone (Thin-film microphone) including a planar polymer film.

In the microphone (NM microphone) using the nano membrane according toone embodiment of the present invention, when a sound pressure isapplied, the nano membrane vibrates between the first and second polymerfilms, triboelectricity is generated by the vibration, and an outputvoltage and a frequency of the generated triboelectricity are measured.

When a central hole of the first polymer film is open as shown in FIG.22A, the nano membrane vibrates smoothly because of a sufficient space,whereas when the first polymer film is planar as shown in FIG. 22B, thenano membrane is bonded to the polymer film and does not vibrate suchthat performance of the microphone may be degraded.

FIGS. 23A to 23C show a result for which the microphone using the nanomembrane according to one embodiment of the present invention isemployed in a voice pattern security system.

The voice pattern security system is a program for registering a voicewaveform of a user using the microphone using the nano membrane,analyzing the voice waveform and a frequency pattern, allowing access ofonly a user whose voice is similar to the registered voice waveform andfrequency pattern.

FIG. 23A is a graph showing a decibel (dB) for each frequency measuredat the microphone using the nano membrane according to one embodiment ofthe present invention when a registrant, an authorized user, and adenied user speak a word “nano membrane.”

FFT was performed on a waveform of a sound input from each of theregistrant, the authorized user, and the denied user.

FIGS. 23B and 23C are graphs showing a dB for each frequency measured atthe microphone using the nano membrane according to one embodiment ofthe present invention when a registrant, one male person, and two femalepersons speak a word “hello.”

Referring to FIGS. 23B and 23C, FFT was repeated ten times on a waveformof a sound extracted from each of four persons, i.e., the registrant,one male person, and two female persons.

A measured dB peak for each frequency was differently measured for eachperson, and thus performance of voice measurement and classification ofthe microphone using the nano membrane according to one embodiment ofthe present invention was experimentally confirmed.

FIG. 24 is a graph showing a result of a comparison test for themicrophone using the nano membrane according to one embodiment of thepresent invention and a commercial microphone.

Referring to FIG. 24, after a registrant speaks a word, voices recordedin the microphone (NM microphone) using the nano membrane according toone embodiment of the present invention and in a commercially availablemicrophone (Commercial microphone: 40 PH G.R.A.S.) were analyzed.

FFT was performed on the voices recorded in the microphone (NMmicrophone) using the nano membrane according to one embodiment of thepresent invention and in the commercially available microphone and dB sfor frequencies were compared, and the comparison results of the dBswere measured to be very similar.

Since a nano membrane according to one embodiment of the presentinvention is transparent and has a thickness of a nano unit, there is anadvantage capable of being easily attached to a 3D surface such as ahuman body.

A speaker and a microphone, which use the nano membrane according to oneembodiment of the present invention, are transparent and can be attachedto the human body such that there is an advantage capable of beingutilized in a wearable device.

Although the description herein has been made in some illustrativeaspects, various modifications and alterations can be made from thescope defined by the appended claims, and the technical scope of thepresent invention should be defined by the appended claims.

What is claimed is:
 1. A speaker device using a nano membrane,comprising: a nano membrane including metal nanowires comprising: aninsulating layer having a predetermined thickness based on a diameter ofeach of metal nanowires and configured to contain the metal nanowirestherein; and the metal nanowires arranged to cross and having portionsof side surfaces which protrude from one surface of the insulatinglayer, wherein the predetermined thickness of the insulating layer isdetermined based on a height of a portion, at which the metal nanowiresintersect, such that the metal nanowires are included inside theinsulating layer; and a voltage portion configured to apply analternating current (AC) voltage to the nano membrane, to generate heatby resistance generated in the metal nanowires, wherein an amplitude ofthe AC voltage and a heating time are controlled according to atemperature T_(s) of the heat to be generated, based on an equationbelow: ${T_{s} = {\frac{{U^{2}{t/R}} - Q_{d}}{C_{m}} + T_{i}}},$ whereT_(i) represents an initial temperature of the nano membrane, Urepresents the amplitude of the AC voltage, t represents the heatingtime, R represents resistance of the metal nanowires, Q_(d) representsdissipation heat, C represents a heat capacity ratio of the metalnanowires, and m represents a mass of the metal nanowires.
 2. The nanomembrane of claim 1, wherein the metal nanowires are arranged such thatthe metal nanowires, of which a length direction is arranged in a seconddirection perpendicular to a first direction, are superimposed on themetal nanowires of which a length direction is arranged in the firstdirection.
 3. The nano membrane of claim 1, wherein the metal nanowiresare connected in a network structure.
 4. The speaker device of claim 1,wherein the voltage portion changes a frequency of the AC voltage everypredetermined period and applies the AC voltage of the changed frequencyto the nano membrane.
 5. The speaker device of claim 1, furthercomprising a frequency measuring portion configured to measure afrequency of an input sound signal per time interval, wherein thevoltage portion changes a frequency of the AC voltage to correspond tothe measured frequency and applies the AC voltage of the changedfrequency to the nano membrane.
 6. The nano membrane of claim 1, theinsulating layer comprises a deposited parylene-C.